This invention relates generally to electronic musical instruments and more particularly to electronic pianos. Specifically, the invention is directed to circuit means for varying the amplitude of the piano characteristic curve envelope in response to the relative hardness with which the piano key is actuated, and for mixing together a fundamental frequency and selected components of harmonics thereof to produce musical tones that correspond substantially to a piano voice.
Heretofore, the manufacturer of electronic musical instruments, particularly those of the electronic piano type, have gone to great lengths to produce a keyboard arrangement which is substantially electronic in nature, free of hammers and strings, but which will electronically reproduce the tones of an actual piano string when struck. Among the problems in so providing electronic piano keyboards is that of producing the proper attack, peak, and decay characteristic curve of a piano voice. This has been closely approximated in the past by providing capacitor charge circuits which operate in response to capacitor discharge circuits so that charge rates and discharge rates of capacitors will produce attack and decay characteristics along an exponential curve. However, this type of electronic piano keyboard is at best an approximation of a real piano string tone.
One of the problems of electronic pianos is that while a close approximation of the actual attack, peak, and decay characteristics of the piano voice is obtained by capacitor discharge and charge circuits, these circuits do not compensate for variations in harmonic tones of the fundamental frequency of the piano string along the piano voice characteristic curve. Therefore, their actual sound is a false representation of a real piano.